Non-living soil organic matter: what do we know about it?

Non-living soil organic matter is a small but critical component of soils contributing to soil structure, fertility and a range of other chemical, physical and biological functions. Although considerable work has contributed to our knowledge of its distribution, chemical structure, mineral associations and turnover, there is still little information on which fractions or pools of non-living soil organic matter are implicated in various soil functions and to what extent. This review paper summarises some of what is known about the distribution, chemistry, mineral associations and soil structure, turnover and the measurement of non-living soil organic matter, with particular emphasis on Australia. It also discusses some of the difficulties in using current methods for describing the function of this material in soil.